Means for controlling brakes on trailer vehicles



NOV. 14, 1944. J RIODWAY 2,362,931

MEANS FOR CONTROLLING BRAKES ON TRAILER VEHICLES Filed Ja.n.'.6. 1943. 3 Sheets-Sheet j. ag 6 '30 7- 7 36 x 5y 1% a 55 v I L 4 I1',

23 I I 2 Z9 21 5 a0 Z6 Z2 Z4 16 f9 Inventor Attorneys v NOV. 14, 1944. J RQDWAY 2,362,931

MEANS FOR CONTROLLING BRAKES ON TRAILER VEHICLES Filed Jan. e, 1943 s Sheets-Sheet? R v 3 4 17 v 35 /5 5? 5 Zy -j Attorneys Nov. 14, 1944. w RO'DWAY 2,362,931

MEANS FOR CONTROLLING BRAKES ON TRAILER VEHICLES Filed Jan. 6, 1943 3 Sheets-Sheet 5 E Cum [Z PEDAL EFFORT PEDAL EFFORT A ttorneyS Patented Nov. 14, 1944 M-EANSI FoR'ooN'm'o TRAILER VEHICLES me nmmsim John Eodway, LincbliigEngland' ApplicationJanual-j 6,

- Claims;

This ,inventionrelates.tomeans for controlling the brakes. on trailerv vehicles and to the kind wherein theeffort applied through fluid pressure assisted servo brake, devices on a tractor vehicle is transmitted also to the brake operating, mechanism; of a trailer vehicle. .e o

Theinvention has particular reference to con trol devicesxwhich operate. to transmit a lesser braking. effort when the trailer is unladen than when; it is loaded, and it is the object of the invention to provide an improved control device ior thisqpurposewhich is ofsimple, androbust construction and which is particularly adapted for use in the direct or single acting air; pressure systemsused oniheavy; motor vehicles.

According to the, invention there IS nected toa source'of fluid pressure on the tractor and a pair of connected pistons or diaphragms provided aioontroldevice; comprising a. valve housing, con- 19'4s,;seriarNannies Inc-Great Britain February 1 7,l-1-942 v when; thefcontrol according to gthe invention is of differential areas mounted within said housing and controlling; the operation of'valve elements inlsuch manner that, when the traileris unladen, a pressure is transmitted. to' the trailen brake actuating means; which isa predetermined proportion of the pressure, available in the main;or i

service line; whereinthe.;vwhole ofthe -movable valve components are-carried byor directly-actuated by thepiston ordiaphragm assembly, hand operatedv means beingprovided, adaptectto. be

used when thetrailerisloaded; for moving'said assembly to and holding it in aposition in which I the valves are-setxto. allow the whole of the pressure. available in thezservice line to be transmitted to thetrailer brakeactuating means.

n Referencewilhnow be made-to the accom'panying drawings-Lwhich illustrate a construction according totheinvention andinwhich: r Fig; 1. isa sectional elev'a tion of a'control-valve for: trailerbrake--mechanismwith the partsin th brakes.oif= position when; the trailer vehicle is 'unladen, f

Fig. 2-isa sectional elevation similar toFigQI, but showing the operative position of the parts when the trailer vehicle is" unladen,

a'ti'veposition of the parts when the trailer vehicle-isloaded',

trol connections,

Fig. 4 is an extemalfelevation showing the om Fig.- 5 is a diagram showing the. relations be.-

trailer brake poy ler used: 1' 1 g Y I In the vconstruction illustrated and referring first to Fig. 1',.a;casing I; contains two pistons .2 andz 3.-.of 'differential areas'theratio between which isqdeterinined: by the ratio between the light and loaded: weights of the trailer vehicl tolwhich the: invention is applied; b

Thexcasing: l hasa port 4 adapted to communicate,;,with a zsource' of fluidpressure on the tractor vehicle;theconnection, to which is shown at; 59in. Fig. 4., The casing 12 has also ports 6 and; 1:, the: port. 6; also communicating-with the I conduitiy5: by' way of a pipe'fl; and the port. 1 communicating; with thetrailer brake cylinders lay way'of' a:.con.duit 9ishowntin Fig. .4. The cas- 'ing is; further provided with a ,fourth port It through which: a chamber I l within-the casing l comm-unicates withatmosphere and which serves as an exhaust port. 'Ihe two pistons 2 and 3 areconnected at; their centralportiQns by a stem l2: having ports l'3 thereincommunicating with ,centralgpassage- IA" within-:the stem opening into a chamber IS-Withinthe casing I. 'Iihesmaller-piston 2 is mounted in a compartzment I6 oiithecasing. Around the open. end of thepassage i4 is vformed avalve seating I! with which'co-operatesa'valve member is carried at oneeend of a rod: I9 movably'mounted in a guide sleeve 2K1 formin part of the casingl and formed near its outer endxwith ports 2| and ;.a valve seatinggz l. The outer 'end'of the rod l9 carries a valve member 23 adapted 'toz-co-operate with the seating 22-,v'the saidigvalve member 23 being irnov ableina chamber Zlqwhichis in permanent communication with the pressure fluid inlet port 6.;

'45 Fig; 3- isa sectional elevation showing the oper- I:

7 The larger piston is-rnormally prevented from movement whichlwould: bring the valve seating Lil-into contact with the valve member I8 by a springtzi; one end: of which bears against the I piston and the other endof which: surrounds the sleeve 20. and: bears; against therecess formed between. the sleeve and thecasing wall. A second .sni i'rig 154 disposed within the; chamber 24 and tends to maintain the ,valvemember 23' on its seat- 22.; v v H v a Withinan-extension Zhof the, centralchamber It is mountedan-adjusting lever 28 pivotally ,rnounted'atZS and projecting through a slot 30 in:- the:c asing wall, its. outer portion being connected by a-rodor cable 3, lto a'manual or pedal operating devicel The lever 23v carries a cam j 321whichbears-againstone.end 33 of a U-shaped arm 34 pivoted at :r: and which "embraces and pivotally; connected; to; the stem IZ-"ati 35.

member I8 and lift valve 23 off its seat to admit pressure fluid through ports 2I to chamber I tion has been described with particular reference to the use of a pair of pistons 2 and 3 these could be replaced by connected diaphragms haying their peripheral portions fixed'to the walls of the casing I but capable of flexing at their central portions to move the seating II towards and away from the valve member I8.

I claim:

1. A device for controlling the brakes of a trailer vehicle, comprising a valve housing,

' means for connecting said valve housing to a The pressure acting on piston 2' causes the valve seat I1 to move into contact with valve until the pressure load on the piston 3 is equal to the pressure load on piston 2. When this point is reached the pistons 2, 3 move slightly to the left followed by the valve rod I9 until both valve members 23 and I8 contact with their seats 22 and I1 respectively as shown in Fig. 2, and the elements will remain in these positions until the pressure operating through port 4 is varied. Under these conditions, the pressure in chambers I5 and IE will be in the inverse proportion of the ratio of the efiective areas of the pistons 2 and 3. By the operations above described the pressure after operating over a short time through the port 6 is cut oil? by the seating of valve member 23 with the result that less braking effort is utilised for the actuation of the brakes than would be the case if free and unrestricted pressure operated through the port I and conduit -9. When the pressure control valve on the tractor is returned to release position and the service line is vented to atmosphere, the pressure in ports 4 and 6 is destroyed thus allowing the pressure in chamber I5 to push the piston 3 and seating I1 away from the valve I8 so that pressure fluid can escape through passage I 4, ports I3, chamber II and port In to atmosphere. The parts are thereby returned to the positions shown in Fig. 1 with corresponding release of the brake effort.

When the trailer vehicle is loaded, the hand control lever 28 is moved towards the right to the position shown in Fig. 3, thereby drawing both pistons 2 and 3 towards the right, seating valve I8 and opening valve 23. Thus, direct communication is established between ports 6 and I so that the pressure applied through conduits 5 and 8 is passed on to the trailer brake applying mechanism undiminished in degree.

Referring now to Fig. 5, curve I shows the relation between pedal effort and trailer brake power on a trailer vehicle operating under normal conditions using a simple reduction valve in the connections between tractor and trailer vehicles. Curve I in Fig. 5 represents conditions when the trailer is loaded, but when the reduction valve is in operation and the trailer is unloaded curve 2 is produced.

Fig. 6 illustrates similar curves obtained by using the valve according to the present invention, curve I corresponding to the loaded condition of the trailer vehicle and curve 2 corresponding to the unloaded condition. By comparing Figs. 5 and 6 it will be seen that whereas the total braking in the unladen condition in Fig. 5 can be the same as that in Fig. 6 yet the pedal effort range corresponding to maximum braking when unladen is very much greater when the present invention is used. This represents a considerable improvement in controllability of the unladen vehicle.

It is to be understood that although the invensource of pressure on a tractor vehicle and to trailer brake applying means respectively, a pair of pistons of differential areas mounted in said housing and having a connection between the central portions thereof, a spring actuated valve member, a seat for said valve member on one of said pistons and communicating with the atmosphere, a fixed seat for said valve member in said housing and communicating with the brake applying means, and manual means operable on said pistons and valve member to cause application of the brakes when the trailer vehicle is loaded.

2. A device for controlling the brakes of a trailer vehicle, comprising a valve housing, a pair of pistons of differential areas mounted in said housing and enclosing between them a space continually open to atmosphere, a central connection between said pistons, a disc valve member movably mounted adjacent one of said pistons, a seat for said valve member on one of said pistons and communicating with said space between the pistons, means for connecting both ends of said housing to a source of pressure fiuid on a tractor vehicle, a second seat for said valve member fixed in the end of the housing adjacent the piston of larger area for controlling the admission of pressure fluid thereto, means for connecting the end of. said housing adjacent the piston of larger area to the trailer brake mechanism, and manual means operable on said pistons and valve member to place the connection to said brake mechanism in free communication with said source of pressure fluid when the trailer vehicle is loaded.

3. A device for controlling the brakes of a trailer vehicle, comprising a valve housing, a pair of pistons of differential areas mounted in said housing, a rigid connection between said pistons, valve components mounted coaxially with said connection, means for applying pressure to both ends of said housing, a port in said housing adjacent the piston of larger area and communicating with the l trailer vehicle brakes, and manual means operable upon said pistons and valve components to admit full pressure to the trailer vehicle when the trailer vehicle is loaded.

4. A device for controlling the brakes of a trailer vehicle,comprising a valve housing, a pair of pistons of differential areas mounted in said housing and enclosing between them a space in constant communication with atmosphere, a valve component mounted centrally of said pistons, a spring opposing movement of said valve component in one direction, an annular valve seat formed on one of said pistons and communicating with said space, a second valve seat formed in an end wall of said housing, said valve seats cooperating with said valve component, means for connecting both ends of said housing to a source of pressure fluid on a tractor vehicle, means for connecting the end of said housing adjacent the piston of larger area and having said second valve seat therein to the trailer brakes, and hand operable means to move said pistons and valve component to a position to admit full pressure to the trailer brakes when the vehicle is loaded.

5. A device for controlling the brakes of a trailer vehicle, comprising a valve housing having means for connecting it to a source of pressure fluid on a tractor vehicle and to the brake applying means of the trailer, a fluid pressure responsive member mounted movably 'in the housing and having differential areas, the smaller area of said member being indirect communication with the means for connecting the housing to said source of. pressure fluid and the larger area of said member being in communication with the means for connecting the housing to said brake applying means, said member having a passage communicating wi h the atmosphere and a valve seat for controlling said passage, a valve element having a component cooperative with said valve seat to control said passage and having a second component, a relatively fixed valve seat cooperative with said second valve component and controlling communication between the means for connecting the housing to said source of pressure said passage and to fluid and said larger piston area and brake applying means, and manually operable means for moving said fluid pressure responsive member into a position to engage the valve seat thereon with the cooperative valve component to close move said second valve component into open position relatively to said fixed valve seat.

' JOHN RODWAY. 

